1. Field of the Invention
The present invention relates to a fuel injection device for an internal combustion engine.
2. Description of Related Art
Conventionally, as a fluid injection device for injecting fluid such as fuel, a device in which a contacting portion of a valve member is seated on a valve seat of a nozzle body or separates from the valve seat in order to inject the fluid intermittently is publicly known, for instance, as disclosed in Japanese Patent No. 3183156. In such a fluid injection device, electromagnetic driving means disposed in an end of the valve member opposite from the contacting portion reciprocates the valve member.
Lately, in accordance with improvement in performance of the engine, improvement of response of the fuel injection device during operation is required. The response of the fuel injection device can be improved effectively by reducing size and weight of the valve member as a movable member.
However, if the whole length of the valve member in an axial direction is contracted to reduce its size, stability of the valve member in the axial direction may be reduced, so the valve member may tend to incline with respect to the axis. If the valve member inclines when the contacting portion is seated on the valve seat of a valve body (the nozzle body), there is a possibility that guiding means may contact the valve member. For instance, the guiding means is formed in the valve body in order to guide the valve member so that the valve member can reciprocate in the axial direction. If the valve member contacts the guiding means, the end of the valve member on the contacting portion side will rotate around a contact point between the valve member and the guiding means (the contact point functions as a supporting point). In such a case, there is a possibility that the contacting portion of the valve member may separate from the valve seat. As a result, sealing performance between the contacting portion and the valve seat may be decreased, and fuel leak may be caused.
The contact between the valve member and the guiding means can be prevented by enlarging a clearance formed between the valve member and the guiding means. However, if the clearance formed between the valve member and the guiding means is enlarged, the stability of the valve member during the operation may be reduced, and variation in fuel injection quantity may be caused.